In a large pot, place the chopped apples, quince, 1/4 cup water, knob of butter, 1tablespoon golden syrup and cook over a low heat until the fruit begins to soften. 20 minutes is good, but check it's not drying out (add more water if so), and that it's not sticking to the bottom.
While the compote is cooking, preheat oven to 180.
In a large bowl, cream the butter and sugar.
Add the egg, golden syrup, flour, baking powder, and milk. Stir to combine and then beat for a few minutes to make light and fluffy.
Spoon the cooked compote into the bottom of a square baking dish (or into several smaller ramekins) and then spoon a layer of pudding mixture on top. If you're using smaller ramekins, you want about 1inch of pudding mix. If it's a whole one, use the whole mix.
Bake 20-25 minutes for individual or 30-35 minutes for whole until sponge is slightly risen in the centre, it feels reasonably firm (you can test with a skewer and see if it comes out clean) and is lightly golden brown on top.
Eat with whatever complements you desire - but don't forget that extra drizzle of golden syrup over hot pudding before you add the other goodies!